In the grinding of crankpins, drive is transmitted to the crankshaft in conventional manner from the headstock and as the crankshaft rotates so a grinding wheel mounted on a wheelhead is advanced in registry with first one and then another of the crankpins so as to grind the crankpin. The wheelhead is advanced and retracted during rotation of the crankshaft so as to maintain grinding contact between the grinding wheel and the crankpin as the latter is rotated eccentrically around the axis of rotation of the crankshaft.
It has been proposed to use end journals to assist in mounting a crankshaft for grinding of crankpins.
Since the circularity of the crankpins will determine the wear characteristics of the crankshaft and the big end bearings associated therewith, it is highly desirable that whatever method of mounting is employed, it should maintain the highest possible accuracy as regards circularity of grinding surfaces of the crankpins. It has been found that whip, and distortion of the crankshaft during grinding may introduce errors in the circularity of the ground surfaces of the crankpins, resulting in accelerated wear and unreliability of crankshafts ground in this manner.
Conventionally when mounted in an engine block, a crankshaft is supported by journal bearings at opposite ends and at intervals along its length. Typically a journal bearing is provided intermediate each crankpin, so that every part of the crankshaft is supported in a journal bearing. Thus a four cylinder engine will typically have five journal bearings for the crankshaft and a six cylinder engine could have as many as seven crankshaft journal bearings.
It is an object of the present invention to provide an improved method and apparatus for mounting such crankshafts in a crankpin grinder to facilitate the grinding of crankpins thereon in a manner which will reduce the circularity errors characteristic of prior art methods, and apparatus for supporting crankshafts in such machines.